In large commercial buildings, recurring electricity costs for lighting can be more than half of the total energy budget. Consequently, there are considerable economic benefits to be obtained through more efficient lighting techniques. For example, simple devices such as motion sensor switches or light timers are often used to reduce wasted energy by reducing unnecessary lighting. Resources can also be conserved by replacing low efficiency ballasts and prolonging the operating lifetime of high efficiency ballasts and other light fixture components.
Many large commercial lighting applications depend heavily on fluorescent light fixtures driven by a ballast. The type of ballast determines, for example, the power consumption and optimal type of lamp to be used in the fixture. Along with characteristics of the light fixture itself, such as the geometry of the fixture, heat management, and the shapes of the reflectors, the choice of ballast and lamp largely determine the gross light production, expected maintenance interval, and energy consumption of the fixture. Consequently, effective lighting redeployment may require changing the ballast and/or type of lamp used in the fixture.
In a traditional light fixture, the ballast is generally hard-wired within the light fixture, and the light fixture is hard-wired to a building power supply. Thus, with the exception of changing the lamp, any maintenance and/or repairs to the light fixture may require the costly services of an electrician. Further, it can be expensive to move, replace, and/or modify an existing light fixture. As a result, existing light fixtures tend to remain in place even when they are obsolete or lighting requirements change, resulting in wasted electrical power and lost productivity due to ineffective lighting. Thus, there is a need for a light fixture which includes a detachable power pack such that the ballasts and other lighting components can be quickly replaced to achieve maximized energy savings. For example, a first power pack including a ballast with a ballast factor of 1.0 may be replaced by a second power pack including a ballast with a ballast factor of 0.75 to reduce power consumption of the light fixture. Further, there is a need for a detachable power pack with latching ends such that the detachable power pack can be securely mounted to and easily detached from the light fixture without the use of tools.
As known to those of skill in the art, ballasts used to supply power to light bulbs can produce a substantial amount of heat. This heat is mostly generated by metal-oxide semiconductor field-effect transistors (MOSFETs) and other electrical components within the ballast. Unfortunately, traditional light fixtures are limited in their ability to disperse the heat generated by ballasts. As a result, the entire light fixture can become hot and the risk of fire due to ballast overheating is increased. In addition, operating a ballast at an elevated temperature decreases the operating lifetime of the ballast, resulting in increased costs to replace ballasts. Further, high temperature operation results in less light energy output because light output is lower when the ballast components and lamps are hot. Thus, there is a need for a light fixture in which heat generated by the ballasts can be dispersed through convective, conductive, and/or radiative cooling.
There is also a need for a light fixture having a removable power pack with an integrally mounted deployable sensor (e.g. for monitoring ambient light level and/or the presence of occupants) that is readily and conveniently movable from a stowed condition (e.g. to facilitate storage, shipping/transport and installation) to a deployed condition (e.g. following installation of the fixture) for control and operation of the light fixture.